"These are found over the southern highlands with a cluster in the northern Hellas region," Carter and Pouldet write.

"The anorthosite exposures are found in the rims of four, 50 to 70-kilometre large craters, as well as in the southern and northern rim of the 140-kilometre large Holden crater."

A second team of scientists led by Dr James Wray of the Georgia Institute of Technology found significant deposits at Xanthe Terra, the large Martian volcano Syrtis Major, and Noachis Terra, which features exposed crater floor bedrock.

"Here, we describe one large region and two smaller locations where felsic materials have been identified," write Wray and colleagues.

"Such feldspar-rich rocks were not anticipated on Mars."

The discovery suggests that similar feldspar minerals identified previously at NASA's Mars Curiosity Rover's landing site in Gale Crater is not an isolated occurrence, and could reflect more widespread magmatic processes on the red planet.

More evidence needed

This is tantalising evidence that the early evolution of the Martian surface and crust is far more complicated than thought, according to planetary scientist, Dr Simon O'Toole of the Australian Astronomical Observatory.

"Maybe our picture of Mars is incomplete, we need to reassess what we think happened in the past, and look for more evidence of this kind of material to get a better global picture," says O'Toole.

"It's a hint that things may not be as they seem, and the early evolution of magma on Mars was different to what we expected, when we just believed the crust was mostly basalt."

If the pooling of magma on Mars was a longer process, materials would crystallize out at different times providing more mineral diversity.

"Seeing these feldspar deposits does suggest that this process took more time," says O'Toole.

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